28Does a greater contact force create more scar? A quantification of the relationship between late gadolinium enhancement on cardiac MR imaging and catheter contact on af ablation

Abstract

Introduction: Catheter-myocardium contact force (CF) is an important determinant of radiofrequency (RF) lesion generation. Novel RF-catheters enable real-time monitoring of CF, but evidence that CF is the primary determinant of lesion quality is lacking in humans. We used late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) to assess the relationship between applied contact force and chronic scar formation. Method: Twelve patients underwent pulmonary vein isolation using a CF-sensing catheter (SmartTouch Thermocool, Biosense-Webster, CA, USA). Ablation position was recorded using the CARTO-3 electroanatomical mapping system. LGE CMR was performed at a median of 7.2 (range 3-11) months post- ablation using an Achieva 3.0T MRI scanner (Philips, Amsterdam, The Netherlands) with a 3D ECG triggered, free-breathing inversion recovery turbo field echo scan sequence. The LGE-CMR images were segmented using Seg3D by an experienced observer. Signal intensities (SI) were projected onto the segmented shell, using a maximum intensity projection and fused to the CARTO-3 shell using an Iterative Closest Point (ICP) algorithm. The two shells (Contact Force and LGE signal) were then compared using custom built software. The shells were thresholded to blind the observer to local variations in LGE SI and CF before paired paths along the ablation lines were manually drawn on the surface of each shell. Results: For 1710 ablation points across 12 patients, there is a small but significant relationship between applied CF and chronic scar formation as indicated by CMR LGE SI (p<0.0001, R2=0.02) and between grouped CF and mean LGE SI (one- ANOVA, p=0.02). For every ablation line, regions are identifiable in which there is a relationship between CF and SI (see figure). Conversely, other regions of the same ablation lines do not show a close correlation between applied CF and resulting scar formation. Conclusions: Post-ablation scar, as assessed by MRI LGE signal intensity, is qualitatively related to CF, and quantitative analysis shows a weak but significant correlation. However, the majority of variation in scar formation is not explained purely by contact force, and may be related to other ablation parameters such as local cardiac anatomy, regional cooling effects and catheter stability. ![Graphic][1] [1]: /embed/inline-graphic-1.gif